The information technology revolution that has taken place over the last fifty years or so has meant that many human activities now involve, and often revolve around the manipulation of information technology systems, and in particular computers. The nature of the interfaces supporting these interactions has evolved continually in parallel with the processing and telecommunications capacities of these systems, from punch cards, keyboards, mouse driven graphical user interfaces and most recently multi-touch touch screen interfaces, the richness and accessibility of information displayed to a user has increased, and the precision and facility of interactions improved. Nevertheless, such operations have systematically remained based on manual interaction with the devices in question.
Meanwhile, human physiology dictates that an individual's eyes be directed at whatever is the object of their attention. In principle, this provides an intuitive and transparent mechanism for interfacing with computers. In practice however, such interfaces have proved difficult to implement, requiring expensive optical hardware, and imposing significant restraints on the freedom of movement of the user in order to maintain satisfactory performance. Nevertheless, advances in technology are increasingly making gaze tracking approaches feasible, particularly in situations where a user must monitor a large number of moving elements in the interface, over a long period, and where the implications of a misinterpretation or failed manipulation of the interface in real time are sufficiently serious to justify the cost of such systems. Examples of such installations include air traffic control displays, head up displays in vehicles, and so on.
The existence in parallel of these two separate modes of interaction calls for effective hybrid interaction mechanisms making optimal use of the inherent strengths of each mode